Due to a appearance of a liquid crystal molecular being similar to a board or a stick, the physical characteristic in the parallel direction and the perpendicular direction of the molecule's long axis are different and so the liquid crystal molecular also is called anisotropic crystal. For nematic liquid crystal, it has two indexes of refraction of no (in a direction perpendicular to liquid crystal long axis) and ne (in a direction parallel to liquid crystal long axis). A single optic axis with two different indexes of refraction (for example: liquid crystal), e.g., birefringence crystal, has the following characteristics: when a non-polarized light passes through the liquid crystal, the light divides into two polarized lights that polarized directions of two polarized light are perpendicular to each other. The speeds of the two polarized lights are different and so the refraction angles thereof are also different. Hence, the liquid crystal can polarize light.
Furthermore, due to the liquid crystal is mobile, the molecular of the liquid crystal can be moved to form different arrangement by a slight force. For example, a nematic liquid crystal can be twisted with an electrical field. When the electrical field does not apply to a liquid crystal panel, the direction of the liquid crystal is decided by alignment layers in an upper and a lower glass substrates of the liquid crystal panel. For twisted nematic (TN) liquid crystal display, the difference in angular magnitude of the directions of the upper alignment layer and the lower alignment layer is angle 90 degree and the direction of liquid crystal from top to bottom rotates with angle 90 degree. Therefore, the light passes one of two polarizers and becomes a polarized light with only one polarized direction, then the polarized light passes through the liquid crystal with rotating angle 90 degree, the polarized and rotated light can pass through the other polarizer. However, an electrical field applies to the liquid crystal panel, the arrangement of the liquid crystal trends to parallel to the direction of the electrical field. The polarized light will not change the polarized direction during passing through the liquid crystal and so the polarized light can not pass through the other polarizer. Hence, the liquid crystal display mainly employs two polarizers and the liquid crystal, and applies different electrical field to different regions for displaying different brightnesses to form an image of demand.
The liquid crystal display can use RGB (red, green and blue) color filter to display the three primary colors, and use different brightnesses of the RGB color in the same pixel mixed to display a color image, even a true color image. However, lights with different wavelengths pass through the liquid crystal and generate retardation between lights due to lights with different wavelengths having different indexes of refraction in the liquid crystal. Due to retardation, the display of an image will different at different viewing angle and so the magnitude of viewing angle is limited. In those conventional arts, a wide viewing angle compensating layer is in the outside of the liquid crystal display for compensating the retardation, but it is impossible that retardations in any of viewing angles can be simultaneously compensated by the compensating layer. Other solving method of retardation is that the incident direction of the light are perpendicular to a surface of the liquid crystal for reducing the retardation between lights with different wavelength, and then a diffusing layer is in the outside of the liquid crystal display to diffuse the light for increasing the magnitude of viewing angle.
In general, the incident angle of the light entering the liquid crystal panel is smaller than 15 degree and the effect of retardation can be ignored. FIG. 1 shows a diagram of the micro-lens array for collimating light in those conventional arts. The light comes from the bottom of the light-guiding array 10, and then the light is gathered by the light-guiding array 10 and passes through the transparent multi-layer 20 (not shown the detailed structure of the multi-layer). Finally, the light is converged by the lens array 30 for focusing the magnitude of refracting angle in 15 degree. However, the size level of the element of the light-guiding array 10 is the minimeter-level and so the light entering the light-guiding array 10 is hard to satisfy the condition of total reflection. Therefore, the efficient of collimated light is insufficient and furthermore the optical loss also occurs due to employing the multi-layer 20 having several material. The property of the arrangement of light-guiding array 10 is also insufficient in uniform and in single-direction. The fiber also can guide light to make the incident direction of the light perpendicular to the surface of the liquid crystal panel but it is hard to assemble on the liquid crystal panel. Hence, the fiber has problems of the process.